1. Field of the Invention
This invention relates to welding technologies and more specifically to a composition for enhancing weld quality.
2. Description of Prior Art
Gas tungsten arc welding (GTAW) is a fusion welding process wherein metallic components are caused to locally coalesce when heated by electrical energy transferred from a nonconsumable tungsten electrode to the work pieces. The heated area is shielded from the oxidizing effects of air by an envelope of inert gas--argon, helium, or mixtures thereof. The process is performed manually or by machine. The resulting welds are of exceptionally high quality in a wide variety of metals which are sensitive to the deleterious effects of welding in an oxidizing environment.
By virtue of inherent arc energy transfer characteristics, simple fusion by conventional gas tungsten arc welding is practically limited to joining thicknesses on the order of 0.12 inch (4.7 mm) or less. Above this thickness, joint preparation, usually a machined groove configuration, is required wherein material is locally removed to reduce the thickness to a practical thickness prerequisite to achieving full fusion penetration of the weld joint. The removed material is replaced by filler material, usually in wire form, added in one or more applications--passes--to restore the material to the desired thickness.
The consequences of such miltipass welds are high total energy input, multiple weld passes long welding time, additional costs associated with joint preparation and filler material, a need for high manipulative skills and/or complex equipment, significant heat-induced effects such as shrinkage and distortion, the increased possibility of the occurrence of interpass defects or undesirable structures, and the increased frequency of repair work to mitigate these conditions.
Inherent in a majority of welding processes is the utilization of an added welding composition which may function to effect metal refinement, atmospheric protection, stabilization of the arc phenomena, as well as weld bead constituency.
Such compositions are generally based on silica, silicates, limestone, clays and many other minerals. Heretofore, little attention has been given to the purity of the components making up these compositions. Often the chemical constitution varies widely, depending upon the source of the chemicals utilized. Even residual constituents will influence the physical and chemical behavior thereof.
As is known, the weight percent of basic components to acidic components influences welding activity in many ways. For example, a basic composition is known to have a gettering effect on sulfur and phosphorus, while an acidic composition enhances slag control during the welding procedure.
Weld enhancers of various types have been known and used throughout many years. Specifically, flux compositions are for brazing, soldering, and some welding processes, excluding GTAW. They are applied to the metal surfaces to be joined and are designed to prevent, dissolve, or facilitate removal of oxides and other undesirable surface substances during welding. Notwithstanding the use of fluxes, welds have a propensity to be inconsistent, nonhomogeneous, and fraught with voids fissures.
Fluxes are mixtures of a variety of compounds including rosin, borax, calcium oxide, silicon dioxide, among many others and are generally varied depending on the type of metal to be joined and the particular joining process to be used. Notwithstanding these great variations, the one flux characteristic that remains constant is that for the flux to perform its function, it must be thoroughly and evenly applied to the entire surface area to be joined. These added flux compositions are not useable with GTAW in that they interfere with the arc action, contaminate the tungsten electrode, and extinguish the welding arc.